Vacuum tube impulse pattern producer



Patented Oct. 30, 1951 VACUUM TUBE IMPULSE PATTERN PRODUCER Oliver T.Francis, Benville, Minn.

Original application January 4, 1345, Serial No. 571,315. Divided andthis application June 24, 1946, Serial No. 678,872

8 Claims. (Cl. 25(l27) This invention relates to vacuum tube impulsepattern producers, and more particularly to vacuum tube circuit meansfor producing desired signal patterns for a signalling system.

This application is a division of my U. S. Patent No. 2,421,022 entitledDuration Impulse Receiver issued May 2'7, 1947.

Various circuits have been proposed for producing signal patterns ofimpulses and spacings of desired duration. In telephone ringer circuits,rotary contacts driven by a constant speed motor have been used. Inanother circuit the discharge RC time element of a condenser has beenproposed to control mechanically movable contacts. Due to inertiaeffects, movable contacts cannot be used in' producing signal patternsat high speeds.

In the art of multiplex telegraphy, unit vacuum tubes conductive at timedisplaced intervals have been used, the signals from these tubesmodulating the transmission medium. Such modulation is accompanied withdifiiculties in view of the fact that a load common to the outputcircuit of all of said tubes has in the past been used. As theconductivity of these unit tubes sometimes overlap, two or more unittubes may be modulating the transmitter simultaneously instead of thedesired one. Such cross modulation of unit tubes renders the signalproduced of poor quality.

It is one of the objects of this invention to provide a high impedanceload for a plurality of unit vacuum tubes conductive at time displacedintervals whereby this deleterious cross modulation may be kept at aminimum.

Another object is to provide a vacuum tube load device, having aplurality of grids in the path of an electron stream, and means forcontrolling the potential of one of said grids by current flowing in oneof said unit tubes and a second of said grids by current flowing througha second of said unit tubes.

Another object is to provide a signal pattern producer, said patterncomprising impulses of desired duration and spacings of desired timelength.

Another object is to provide a producer of a signal pattern having steepwave fronts without use of excessive amplification.

These and other objects will become apparent from the claims,description and figures in which:

Fig. 1 illustrates an impulse pattern producer embodying my inventionand,

Fig. 2 shows signal patterns which may be produced by Fig. 1. r I

Referring to Fig. -1, I have shown a means for producing-time displacedimpulses of variableduration andspacing,- comprising a means forproducing a source ofvoltage varying in mag nitude, and a plurality ofvacuum tubes each of said tubes being conductive between differentmagnitudes of said.- voltage, for producing'thepatterns of signalvoltages such as shown in Fig. 2.

The source of variable voltage consists of a neon tube oscillatorcomprising the series connection of a B battery I, a gas dischargedevice 3, and the parallel connection of condenser 4 and resistance 5.The grid of vacuum tube 6 is connected to the positive terminal ofresistance 5. The'output circuit of tube 6 can-be traced from thepositive terminal of battery -I, pri-- mary or" transformer 1, plateimpedance oftube.

6, to the ground 2 terminal of battery 1. The

grid of vacuumtube 8 is connected throughresistance 25,- and-thesecondary of transformer- 1 to the negative terminal of battery- I.Theoutput circuit of tube =8-can be traced irom'the' positive terminalof battery 1, through plate impedance of tube 8, potentiometer It, theplate. impedance of vacuum tube H to the negative terminal of battery 1.Vacuum tube II isa screen grid tube and has a high A. C. plate tubecircuits conductive to'input voltages between predetermined magnitudesare known. I prefer to use the pentagrid converter type as described inmy U. S. Patent No. 2,435,579 issued February 10, 1948. The first gridof tube i3 is connected through resistance 20 to a point onpotentiometer- I9. terminal of battery I through resistance 2l,andto thenegative terminal of battery I through voltage divider 14. Its cathodeis connected to ground 2.- Itsscreen grid is connected to a terminal ofbattery I more positive than ground. Its fourth grid is connected to anintermediat point on voltage divider l4.

Similarly vacuum tube l2 has its first grid connected through resistancel9, topotentiometeri I0 near the cathode of tube 8. Itscathodefis.

Its anode grid is connected to the positive.

connected to ground 2. Its anode grid is connected through resistance 26to the positive terminal of battery I, and through voltage divider I tothe negative terminal of battery I. Its fourth grid is connected to anintermediate point on voltage divider I5.

Since tubes I2 and I3 both have high A. C. plate impedances it isessential to efficiency that the load in their output circuits be ofhigh A. C. impedance also. This load consists of a vacuum tube I6 whichmay be of the pentagrid converter type. Its cathode is connected to thenegative terminal of battery I1. Its first grid is connected throughresistances 21 and 22 to the positive terminal of battery I7. Its anodegrid may be left disconnected. Its third and fifth grids are connectedtogether internally and to the positive terminal of battery I1. Itsfourth grid is connected through resistances 28 and 23 to the positiveterminal of battery II.

The output circuit of tube I2 can be traced from the positive terminalof battery I, plate impedance of tube I6,battery I'I, resistance 22,plate impedance of tube I2 to the ground terminal of battery I. w 7

The output circuit of tube I3 can be traced from the positive terminalof battery I, through the plate impedance of tube I6, battery II,resistance 23, plate impedance of tube I3, to the ground terminal ofbattery I. Resistance 24 is connected between outgoing line I8 andground 2.

The operation of Fig. 1 in producing signal patterns such as shown inFig. 2 is as follows. Gas discharge device 3 breaks down at a frequencydepending on the constants of the neon oscillator circuit chargingcondenser 4 and impressing a positive potential on the grid of tube 6,causing a surge of current through the primary of transformer I and apositive potential of brief duration to be impressed on the grid of tube8 through resistance 25. Condenser 9 is charged through the plateimpedance of tube 8.

When condenser 9 is fully charged a P s tive potential is impressed onthe first grids of tubes I2 and I3, rendering them non-conductive toplate current. The reason that tube I3 is nonconductive to plate currentwhen a positive potential is impressed on its first grid throughresistance 20 is that a large current flows from the positive terminalof battery I through resistance 2I, to its anode grid and cathode, pro

ducing a large voltage drop across resistance 2|, a portion of whichvoltage drop is applied to its fourth grid by voltage divider I4.

As condenser 9 discharges through potentiometer I0 and the plateimpedance of tube H the first grid of tube I3 assumes a slightlynegative potential with respect to its cathode. The voltage drop acrossresistance 2| is decreased, and the fourth grid of tube I3 assumes apositive potential with respect to its cathode. The fourth grid of tubeI3 being positive and its first grid slightly negative a current passesfrom the positive terminal of battery I, through the plate impedance oftube I6, battery I'I, resistance 23, the plate impedance of tube I3, tothe ground terminal of battery I, until its first grid is sufiicientlynegative toblock current. The voltage drop across resistance 23 becomesmore than the voltage of battery II. The fourth grid of tube I6 becomesnegative with respect to its cathode, and its plate impedance becomesvery high. The cathode of tube I6 becomes further negative with respectto positive terminal of battery I, resulting in a decrease of currentthrough resistance 24 and lowering of potential of line I8, whichlowering is hereinafter referred to as a negative impulse. It istherefore apparent that when either of tubes I2 or I3 are highlyconductive the potential of line I8 is lowered, that is a negativeimpulse is impressed on line I8. When both tubes I2 and I3 are in ablocked condition, the potential of line I8 is approximately that of thepositive terminal of battery I, since under that condition the plateimpedance of tube It is very small, all of its grids being positive, anda large current flows in the circuit comprising positive terminal ofbattery I, plate impedance of tube It, battery I'I, resistance 24,ground 2. Line I8 constitutes a transmission medium for transmitting asignal to a utilization circuit, such as for example, a receiver of thetype shown in Fig. 2 of my U. S. Patent No. 2,421,022, of which thiscase is a division. The duration of this negative impulse depends onwhere the fourth grid of tube I3 is connected to voltage divider I4. Ifit is con-" nected to the lower portion of voltage divider I 4 the firstgrid of tube I3 must be further negative to block current producing avoltage dropacross resistance 2I and tube I3 is conductive to platecurrent for a shorter period such as shown in pattern I25 of Fig. 2between TI and T2. If on the other hand the fourth grid of tube I3 isconnected to the upper portion of voltage divider I4, tube I3 isconductive to plate current over a greater magnitude of voltage variation of its first grid, producing a'negative impulse such as shown inpattern I21 of Fig. 2 between T9 and T6. It is apparent that desiredpatterns such as shown in Fig. 2 canbe produced across line I8 andground by keying the points where the fourth grids of tubes I2 and I3connect to their respective voltage dividers I5 and I4, and the pointwhere the first grid of tube I2 connects to potentiometer I0.

To further clarify the operation of my inven tion the specific values ofone of the circuits used in tests will be described. It will beunderstood, however, that my invention is not limited to the specificvalues of circuit elements, or to elements of the same order, but onlyas defined in the appended claims.

The positive terminal of battery I was plus 175 volts with respect toground. Its negative ter-' minal was minus volts. Battery II was 22volts. Vacuum tubes II, I2, I3, I6 were 2A7." Tube 6 was a 27. Tube 8was a 2A5 connected as a triode. Gas tube 3 was an 874. Transformer 1was a small audio transformer. Re sistances I9, 20, 25, 21, 28 were tenmegohms each. Resistances 2|, 22, 23, 26 were 100,000 ohms each.Resistance 24 was a quarter megohm. Resistance 5 was two megohms.Resistance Ill was three 50,000 ohm resistors connected in series (totalresistance 150,000 ohms). Potentiometers I4, I5 were ten megohms each.Condenser 4 was .05 microfarad. Condenser'9 was .006 microfarad. Eachtime gas tube 3 broke. down condenser 9 was charged as a result of thepositive pulse impressedon grid of tube 8 from secondary of transformerI through resistance 25. As condenser 9 discharged tube I3 would firstbecome conductive and then block. Tube I2 would then become conductiveand then block. As a result two negative impulseswere impressed on lineI8, the duration of each impulse being readily regulated by varyin itscorresponding potentiometer (I4or I-5). The dura- 52 t en. of ac fthese. mpu se was measured yvarieu We n w t pes f mpuls r ceivers- Qne pi pul r v r us d f r su hmeas uremen-ts is described in my U. S.PatentNo. 2,399,668 issued May 7, 1946. A

It is obvious that my invention may take widely different forms; fromthose illustrated without departing from its spirit, and it is to belimited in scope only as defined in the following claims. I

What I claim is: I

1. In a signal pattern producer of a plurality of impulses and spacingsof desired different duration for controlling a signal impressed on'avline, .a plurality of vacuum tube valves each having an anode and acathode, means for render-. ing the anode cathode path of a" first ofsaid valves .conductive for .a first portion of-a signal period, meansfor rendering the anode cathode path of a second of said valvesconductive for a second portion of said signal period, a load for saidvalves, said load comprising a vacuum tube having a plate, oath-odeelectrode and a plurality of grids, a positive biasing source, aplurality of resistances, means for connecting said biasing source, afirst of said resistances in the common circuit of said plate, saidcathode electrode, a first of said grids, the anode and cathode of afirst of said valves, means for connecting said biasing source, a secondof said resistances in the common circuit of said plate, said cathodeelectrode, a second of said grids, the anode and cathode of a second ofsaid valves, and a line connected to said cathode electrode.

2. In a Vacuum tube circuit, a plurality of vacuum tube valves, meansfor varying the current in each of said valves with a diiferent signal,each of said valves having an anode and a cathode, a load for saidvalves, said load comprising a vacuum tube having a plate, cathodeelectrode and a plurality of grids, a, first resistance connected in thecommon circuit of said plate, said cathode electrode and a first of saidgrids, a second resistance connected in the common circuit of saidplate, said cathode electrode, and a second of said grids, means forconnecting said plate, cathode electrode and said first resistance inthe circuit of said anode and said cathode of a first of said valves,means for connecting said plate, cathode electrode, and said second ofsaid resistances in the circuit of said anode, and said cathode of asecond of said valves.

3. In an impulse producer for controlling a signal impressed on atransmission line, a source of input voltage variable at a predeterminedrate, a vacuum tube having a, plate, an anode grid, and a plurality ofcontrol electrodes, a load in the circuit of said plate, a load in thecircuit of said anode grid, means for applying said voltage to a firstof said control electrodes to permit current to flow through both ofsaid loads, means for applying a portion of the voltage variationsproduced across said load in the circuit of said anode grid to a secondof said control electrodes to block current in said plate circuit, assaid input voltage increases beyond a predetermined magnitude, and atransmission line connected to said plate load.

4. In an impulse producer for controlling a signal impressed on atransmission line, a source of input voltage variable at a predeterminedrate, a vacuum tube having a plate, an anode grid, and a plurality ofcontrol electrodes, a load in the circuit of said plate, a load in thecircuit of said aning a portion .of the voltage producedacross said.load in the circuit of said anode grid to a second ofsaid controlelectrodes to block current in said plate circuit as said input voltageincreases be yond a predeterminedmagnitude, means for vary ing themagnitude of said portion to vary the due ration of said impulse, and a,transmission line' connected across said plate load. v

:5. An impulse producer: for controlling-asignal impressed on atransmission medium, compris-v a. source of inputvoltage variable at apredetermined rate, a vacuum tube circuit having a plate, cathode sourceof electrons, :anode electrode, a first grid control means forcontrolling space current from cathode source to said plate and saidanode electrode, a second grid control means for controlling spacecurrent from said cathode means to said plate, an anode load in thecircuit of said anode electrode, means for applying said voltages tosaid first grid means to permit current to fiow through both of saidloads. means for applying a portion of the voltage variations acrosssaid anode load to said second of said grid means to block currentthrough said plate load for input voltages above a predeterminedmagnitude, and a transmission medium connected across said plate load.

6. An impulse producer for controlling a signal impressed on atransmission medium, comprising: a source of input voltages variable ata predetermined rate, a vacuum tube circuit having a plate, cathodesource of electrons, anode electrode, a first grid control means forcontrolling space current from said cathode source to said plate andsaid anode electrode, a second grid control means for controlling spacecurrent from said cathode means to said plate, a plate load, an anodeload in the circuit of said anode electrode, means for applying saidvoltages to said first grid means to permit current to fiow through bothof said loads, means for applying a portion of the voltage variationsacross said anode load to said second of said grid means to blockcurrent through said plate load for input voltages above saidpredetermined magnitude, means for varyin said portion to vary theduration of Said impulse, and a transmission medium connected to saidplate.

7. In an impulse pattern producer for controlling a signal impressed ona transmission medium, a source of input voltage variable at apredetermined rate, a plurality of units, each comprising a vacuum tubehaving a plate, an anode grid, and"a plurality of control electrodes, aload in the circuit of said plate, a load in the circuit of said anodegrid, means for applying said voltage to a first of said controlelectrodes to permit current to flow through both of said loads, meansfor applying a portion of the voltage produced across said load in thecircuit of said anode grid to a second of said control electrodes toblock current in said plate circuit as said input voltage increasesbeyond a predetermined magnitude, said load in the circuit of said platecomprising a second vacuum tube having a plate, cathode electrode, aplurality of grids, and a plurality of resistances, means for connectinga first of said resistances in the common circuit of a first of saidgrids, said plate, cathode electrode of said second tube, and the platecircuit of a first of said units, means for connecting a second of saidresistances in the common circuit of afsecond of said grids, said plate,cathode electrode of said second tube and the plate circuit of a secondof said units, and a transmission medium connected to said cathodeelectrode.

8. In an impulse pattern producer for controlling a signal impressed ona transmission medium, a plurality of thermionic valves, means forrendering each of said valves conductive at time displaced intervals,each of said valves having an internal impedance, a load for saidvalves, said load comprising a vacuum tube device having aplate, cathodeand a plurality of grids, means for. controlling the potential of afirst of said grids with a first of said valves, said means comprising aresistance connected in the common circuit of.said plate, cathode, afirst of said grids and said internal impedance of a first of saidvalves, means for controlling the potential of a impedance of a secondof said valves, and a transmission medium connected to said cathode.

OLIVER; T. FRANCIS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,106,342 Doba Jan. 25, 19382,190,504 Schlesinger Feb. 13, 1940 2,248,549 Schlesinger July 8, 19412,413,440 Farrington Dec. 31, 1946

